Research in the Smith laboratory focuses on uncovering the mechanisms that drive development and regeneration in Chordates, a group of animals that includes the vertebrates, tunicates, and cephalochordates . Chordates share a common body plan that is defined by number of unique tissues and organs, including the notochord and a tubular central nervous system (CNS) with a distinct three-part organization (forebrain, midbrain, hindbrain/spinal cord). As an experimental model we use tunicates, which are invertebrate Chordates. Tunicates occupy the unique position of being the closest extant relative of the Vertebrates, the group of animals to which humans belong. Although there are several thousand tunicate species, only a handful are used experimentally. The most widely studied tunicate is the ascidian Ciona.
While tunicates and vertebrates have highly similar embryology, anatomy and physiology, the tunicates have several unique features that make them ideal experimental animals. Most significantly, the tunicates are much less complex than vertebrates, which is evident at scales ranging from anatomical to genomic. For example, the end-product of tunicate embryonic development is the larva, which in Ciona is composed of only 2,000 cells. Moreover, the developmental of the larva follows a fixed and well-characterized cellular lineage. The larval organs and tissues typically contain only dozens to hundreds of cells. Equivalently-aged vertebrate embryos would have more than an order of magnitude more cells. This reduced embryonic complexity allows us to image, manipulate, and model morphogenesis at a whole-organ or whole-embryo level. For example, the Ciona neural plate and notochord each consist of only 40 cells.